Edward w



(No Model.)

E. W. SERRELL.

BRIDGE.

No. 445,302. Patented Ja.11.Z7,l891.

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STATES PATENT OFFICE.

EDW'ARD IV. SERRELL, OF YE7 YORK, N. Y.

BRIDGE.

SPECIFICATION forming part of Letters Ratent No. 445,302, dated January 27, 1891.

Application filed October 27, 1890. Serial No. 369,493. (No model.)

To all whom t may concern.-

Beit known that I, EDWARD W. SEERELL, a citizen of the United States, residing in the city, county, and State of New York, have invented an Improvement in Bridges, of which the following is a specification.

In suspension-bridges the cables, being of metal, expand and contract longitudinally, and as the roadway is suspended from these cables it changes its shape from time to time and in cold weather is very much higher in the middle than it is in warm weather, so that in suspension-bridges of large span the center of the bridge will rise and fall several feet under the action of changes of temperature, the ends of the cables remaining in the same position at the anchorage as has heretofore been the ca se. This has disadvantages, because in railwaybridges the grade of the track is changed very materially, so that in cold weather especially a locomotive is unable to draw its regular train up the incline, and this necessitates the use of either another locomotive or the separation of the train into sections for crossing the bridge; and there is a still more serious diiiiculty in connection with iron suspension^brid ges, which arises from the fact that almost all of suoli bridges require to be stiitened by trusses which should bear their proper proportion of the work of distribution; but when the cables have contracted under less than the average temperature the trusses are lifted by the cables, and to that extent the strain is thrown across the trusses and the cables have extra work to do and the trusses are unduly strained, and when the temperature is higher than the average the strain is reversed. Y

For the betorementioned reasons it has heretofore been almost impossible to reliably combine suspension-cables with trusses or girder-bridges.

The present invention relates to the method ot' maintaining the suspending cables in bridges in their normal positions by compensating mechanically for the variations in the lengths of such cables.

In carrying out the present invention the bridge is to be regarded the same as a machine, subject to the manipulations of an attendant, so that the entire structure will be controlled by suoli atten dant and maintained in its normal position and condition regardless of the changes of temperature.

This invention is available with any susn pension -bridgeg but it is more especially adapted to structures having wire cables passing over elevated towers and trusses or gird ers to distribute the moving load.

The principles involved in my method relate to the combination, with the cables, of mechanical compensators for varying the positions of the cable-bearings, so as to maintain the line of the roadway in a uniform position, notwithstanding the expansion and contraction of the cables. These mechanical appliances acting upon the bearings for the cables will be varied to suit the bridge, and they are to be under the control of the attendant and in such a manner that when the cables contract by change of temperature the bearings can be moved mechanically to elongate the operative length of the cables and maintain suoli cables in their normal position, and when the cables expand by increase of temperature the reverse operation is performed, and it is advantageous to provide upon the bridge proper sights within the vision of the attendant, and which sights are illuminated at night, so that by observing these sights the mechanical appliance can be actuated to maintain the structure of the bridge in a uniform position, and in so doing each part of the structure will take its proper proportion of load, and the risk of injury is lessened, and the grade of the roadway remains unchanged, andlocomotives and other traction appliances can draw over the bridge regular standard loads without being interfered with by changes in the elevation or depression of the roadway.

In the drawings I have illustrated my present improvement.

Figure l represents a combined suspension and truss bridge with double cables, truss, and girder. Fig. 2 is a section at the anchorage, illustrating a device for moving the bearing for the cables; and Fig. 3 is a sectional plan view at the line @c As before stated, the truss or girder A of the bridge may be of any desired character, and the cables B are to be two or more in number, according to the character of the bridge, and they pass over elevated saddles IOO or bearings C of any usual or desired character, and the anchorage of the cables will be varied according to circumstances.

The mechanical adjustment forvarying the positions of the cable-bearings may be made at any suitable place. When such adjustment is applied between the anchorage D and one of the elevated saddles, the adjustment is conveniently effectedvby varying the position of the bearing E at the angle between the vertical anchorage and the cable. This adjustment of the bearing is preferably effected by hydraulic power, as the same is very easily controlled by an attendant.

d represents a pipe from a suitable pump, leading to the hydraulic cylinder h, inwhich is a ram c, acting against the bearing E to vary the position of the, same and thereby compensate expansion or contraction in the cable B, and it is to be understood that an appliance of this kind can be used at both ends of each cable or only at one end ot` each cable, and that water or other suitable liquid is to be pumped through the pipe d bylcompetent power, and that the admission of liquid under pressure through such pipe d is to be controlled by the attendant for taking up the cable as it expands, and the fluid is to be allowed to escape from the cylinder 71, as the cable contracts.

The hydraulic or other power may alone be depended upon for moving the cable-bearing to maintain anormal operative length to the cable, or a wedge corwedges may be made use of between a rigid bearing K and the cable-bearing E, which wedge or other suitable appliance is to be moved endwise by a screw g or other power that is under the control of the attendant, and such wedge may be counterpoised by the weight F, so. that the power required to move such wedge may be lessened, and it is to be understood that as the cable contracts the wedge or wedges c can be withdrawn progressively and then the fluid allowed to escape from the cylinder h to allow the cable-beariugE to rest upon the wedge or wedges until another adjustment becomes necessary by a change of temperature In cases where the adjustments are applied to the elevated saddles such adjustments should be moved by hydraulic or similar power in opposite directions and simultaneously, so as to raise or lower the saddles bodily and without strain upon the tower or structure supporting the saddle or saddles.

It will be apparent that the wedges intervening between the movable bearing and the rigid supports may be made use of in sustaining the cable while the hydraulic ram and cylinder may be undergoing repairs or changes, and in comparatively small structures screws might be' substituted for the hydraulic rams.

This improvement allows for adjusting the suspending cables or chains'under whatever circumstances they may be employed in bridges, and with structures that contain girders, trusses,or stiftening-braces each partwill be caused to bear'its normal strain by the mechanical adjustment sapplied to the cable.

In cases where an accumulator P is provided the pressure in the same and in the hydraulic cylinders may be regulated so as to adapt the pressure to the bridge and causel the hydraulic rams to operate automatically in taking up the slack of the cables resulting from expansion and the reverse. In this case it will only be necessary to pump into the accumulator from time to time to maintain the standard pressure and compensate for leakage. The connection Q between the accumulator and the hydraulic cylinders should be closed automatically by a load passing upon the bridge and opened as the load passes off, so as to preventthe additional load varying` the action of the automatic device.

The accumulator is shown at P, and a pump at R, and the cock Q-in the pipe d between the accumulator and the hydraulic cylinders may be closed by hand by the attendant as a train is approaching the bridge, or by the passage of the locomotive depressing a rail or other device S, connected with the cock, and a reversely-acting device at the other end of the bridge acts to open the cock automatical'ly.

I claim as my invention-- l. The method herein specified of maiutaining a bridge structure having sustainingcablesV in substantially aconstant position by applying a force independent of the bridge itself for moving one or more of the bearings for the cable or cables to compensate expansion or contraction, substantially as specified.

2. The combinatiomwith a bridge structure having trusses and sustaining-cables, of movable bearings for such cables and devices actuated by mechanical power for moving such bearings to compensate expansion or contraction in the cables, substantially as set forth. s

3. The combination, with a truss and sustaining-cables in a bridge structure, of movable bearings for such cables between the tower and the anchorage and mechanical appliances for varying the positions of such movable bearings to compensate expansion or contraction in the cables, substantially as set forth.

4.' The combination, with a bridge structure having sustaining-cables, of movable bear.- ings for such cables and a hydraulic cylinder and ram for moving such bearings and maintaining the bridge structure in a normal position by compensating expansion or contraction, substantially as set forth.

5. The combination, with a cable in a bridge structure, of a hydraulic cylinder and ram and a bearing moved by such ram and a wedge between the movable bearing and a rigid structure for lsupporting said bearing independent ol the hydraulic ram, substantially as set forth.

IOO

IIO

6. The conibiiiation,\vitl1 the bridge structure having cables, of hydraulic cylinders acting to take up slack caused by expansion and the reverse, an accumulator containing a liquid under pressure, and a connection between the .accumulator and the hydraulic cylinders, substantially as specified.

7. The combination, with the bridge structure having cables, of hydraulic cylinders acting to take up slack caused by expansion and the reverse, an accumulator containing` a liquid under pressure, a connection between the accumulator and the hydraulic cylinders, and a Valve in the connecting-pipe actuated automatically or by hand, substantially as specified.

Signed by me this 23d day of October, 1890.

EDVARD XV. SERRELL.

Witnesses:

GEO. O. BEACH, C. W. TOWN. 

